A straightforward double intramolecular cyclization of dibenzyl dichalcogenols into a triple bond

The intramolecular cyclizations of four types of dibenzyl chalcogenols, which contained one or two ethynyl groups, were carried out. Either the double 5-exo or 6-endo-dig mode ring closure reaction regio- and stereoselectively proceeded to give the corresponding symmetrical bis(benzo[c]chalcogenophene) or bis(isochromene) derivatives from the dibenzyl chalcogenols having a diyne moiety. In contrast, the regioselective tandem 5-exo-dig mode intramolecular ring closure reactions of dibenzyl thiol and selenol having a mono-yne into a triple bond gave the trans-biisobenzothiophene and selenophene as the sole product. However, the similar cyclization of dibenzyl tellurol proceeded in both tandem 5-exo and 6-endo-dig modes to afford the trans-biisobenzotellurophene and ditellurachrysene in good yields with the ratio of 1:1. The X-ray structural analysis of these novel compounds is also presented.

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